The sei
(pronounced "say") whales are among the more elusive
of the larger whales, not coming very close to land
at any time and not forming large groups or "schools".

They are found like many
whales in both Northern and Southern hemispheres following
the best feeding at different times of year. Only the larger
older individuals tend to go very far south, they are relatively
rare in Antarctica.

Sei whales favour temperate,
deep offshore waters more so than other species of large
whale, being rarely seen inshore. In the summer months,
sei whales do not move as far towards the polar waters as
other rorqual whales and do not usually enter icy water.
This this way the large rorquals avoid competition for food
resources, each having different feeding grounds, habitats
and prey preferences. They skim feed on copepods (zooplankton)
and other small prey, rather than lunging and gulping, like
other rorquals. This largely explains the relative fineness
of the baleen fringes and the shortness of the throat pleats
in this species.

Sei whales
have less and relatively shorter ventral throat grooves
than blue, fin or minke whales, from 30 to 60, and reaching
down to midway between the flippers and the navel. The largest
baleen plates measure 75-80 cm and there are from 300 -
400 on each side of the jaw.

The back is
often mottled with scars - probably from cookie-cutter shark
bites.

Ecology
and Behaviour

Sei whales are often
seen in groups of two to five. They are fast swimmers,
possibly the fastest of all cetaceans (whales and dolphins)
reaching 50 kmh (31 mph) over short distances.
When slow moving Sei whales surface, their blowholes and
dorsal fin are often visible above the water at the same
time. Feeding Sei whales tend to dive and surface in very
predictable series, often remaining visible just below the
surface between breaths.

Calving occurs in midwinter,
in low latitude portions of the species' range.

Sei whale mother
and calf - picture courtesy NOAA

Sei whale surface feeding, note the extended throat
due to the pleats allowing the skin to extend.Photo- courtesy NOAA